Use of Inserts for Fasteners

摘要

Inserts are normally used in materials that are much softer than the assembly fasteners. Since the hard fasteners can destroy the soft threads during installation or disassembly, it is desirable to install an insert, which has hardness close to the fastener hardness. This insert can be a threaded bushing with the internal thread to mate with the fastener and a larger external thread to spread the load over a much greater area in the soft material. For plastics, the metal inserts are usually molded in place or ultrasonically tapped, and some are tapped by deforming the material in the drilled hole. Inserts can have locking devices to hold them in place, and are even available in a "floating" configuration to allow for fastener hole mismatches, Inserts are frequently used for blind or through tapped hole installations. However, they are much more expensive to use than a bolt and nut in a through hole.